.controls {
    padding: 30px 0 15px;
    text-align: center;
}

.controls .btn {
    margin-bottom: 15px;
}

#waveform {
    position: relative;
}

#progress-bar {
    position: absolute;
    z-index: 10;
    top: 50%;
    margin-top: -10px;
    left: 5%;
    width: 90%;
}